GWT - how to build a tree that dynamiclly bring the sons from the server?

I'm new to GWT , and I want to create a tree that every time that a node is opened (the user clicked on "+" next to开发者_StackOverflow社区 the node) , the actions calls a service with the node id , and the returned results is the list of sons.

Which Class do I need to extend in order to change the behaviour of the "expand" action?

Also , can this be done via smartgwt? How?

Thanks

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See the "dynamiac tree" in http://gwt.google.com/samples/Showcase/Showcase.html#!CwTree (click on "source code" to see the source of the sample.

You might also be interested in http://gwt.google.com/samples/Showcase/Showcase.html#!CwCellTree CellTrees are a bit more complex (and thus harder to grasp) but they perform much better than Trees.